Toyota Prius: specs in the city

Needham, MA—After driving the Honda Insight hybrid gas/electric car (see DN 10/2/00, p. 37), I was looking forward to comparing it to the similar technology in Toyota's Prius.

The Prius uses a parallel gasoline/electric powertrain, while Honda's driveline is a series configuration with a thin-disk electric motor mounted between the engine and transmission case. Toyota designers put two motor generators (MGs) in their powertrain, mounted within the transaxle: The first MG starts the car and recharges the high-voltage nickel metal hydride battery; the second augments the internal combustion engine power and regeneratively brakes the vehicle, enhancing brake effectiveness and reclaiming energy. Under heavy load, recharge output of the first motor generator will be diverted to the second for additional motive power. Unlike the Honda, in some modes electric power alone propels the car.

On the road again. Once seated, what strikes you most is the center digital display just below the windshield for the speedometer and other information. This is not too much of a distraction since the central location in such a small car is not far off the driver's line of sight. But at night, until you get used to it, looking straight at the dark panel feels as if you're staring into a black hole. I found the light from the speedometer display at night casts too much glow on the inside of the windshield. But adjusting this to an acceptable level also lowers the center console controls lighting, so much in fact as to make them unreadable to my eyes. Separate lighting controls could solve this.

The dash-mounted "locomotive lever" for selecting automatic transmission modes is only electronically tied to the powertrain, except for a mechanical pawl that is engaged when in park. This lever tended to block my view of the left side controls on the center panel.

Heading on the highway, the Prius drives comparably to a typical compact with somewhat better low-speed acceleration (you can even spin the wheels starting off in the rain), because an electric motor has greatest torque at zero speed. What takes getting used to is the gasoline engine being shut down, which is mainly noticeable when accelerating briskly from an electric-only cruise. The gas engine uses an Atkinson cycle—high compression with special intake valve timing to extract more power from the power stroke. As a result, the car must use 91 octane gasoline. Engine revs are limited to 4,500 rpm to keep friction losses low.

In 272 miles of mostly suburban driving, my mileage was 43.8 mpg. While an improvement over the all-gasoline Toyota Echo (EPA mpg rated at 31 city, 38 highway, but with an MSRP of only $11,780 for a four-door automatic), the Prius really shines in the city. On a 14-mile stretch, including Boston's Big Dig, the Prius efficiently balanced power, much of it on low-speed electric drive, to give 50 mpg.

In comparing the Prius with the two-seat Insight, the Toyota seems a more elegant design, having the twin motor generators optimized for their tasks. And being able to run solely on electric power offers more flexibility in lowering overall energy use. Because the electric power is integrated into the transaxle, extension of the system with an all-electric drive on the rear wheels could allow an all-wheel drive hybrid platform in the future.

Other likes: Prius is practical with fairly comfortable upright seating for up to five and a real trunk.

Other dislikes: It's based on the pug-ugly Echo, but with more colorful paint. If you want one, get it soon. According to Greg Marchand, field technical specialist with Toyota's Boston Regional Office, after getting the hybrid infrastructure in place, Toyota plans on hiking the $19,995 MSRP a few thousand to try and recover the true cost of the battery, which hopefully will be dropping with increased production—as of late last year the company was losing about $10,000 a car with the battery reportedly costing $4,000.

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